Chicago police violated the Fourth Amendment through a “pattern or practice of use of excessive force,” Attorney General Loretta Lynch declared Friday, revealing the results of a wide-ranging investigation that the city’s former top cop called biased from the start.

The U.S. Justice Department launched its yearlong review of the 12,000-officer force — one of the nation’s largest — in December 2015 after the release of a dashcam video showing a white police officer shooting a black teenager, Laquan McDonald, 16 times as he walked away holding a small, folded knife. The video of the 2014 shooting, which the city fought to keep from being released, triggered widespread protests.

Among other findings, the report determined that city police used excessive force and that “this pattern is largely attributable to systemic deficiencies within CPD and the city.” It also cited insufficient training and a failure to hold bad officers accountable.

“The resulting deficit in trust and accountability is not just bad for residents — it’s also bad for dedicated police officers trying to do their jobs safely and effectively,” Lynch told reporters during a news conference in Chicago.

Former Chicago Police Superintendent Garry McCarthy told Fox News the Justice Department never interviewed him for its report, even though he was on the force until late 2015. Speaking to “America’s Newsroom,” he suggested it was because “my narrative doesn’t fit what they want to say. … The politics is the strongest pull.”

Lynch said her department tried reaching out to McCarthy, but “he was unavailable.”

McCarthy said the actions of police were not to blame for Chicago’s skyrocketing violent crime rate. Last year saw nearly 750 killings across the city, a spike of more than 250 from 2015. More than 650 of last year’s homicides were shootings.

The former superintendent told Fox News last week, “The police are not the problem. The criminals are the problem.”

Under President Obama, the Justice Department has conducted 25 civil rights investigations of police departments, including those of Cleveland, Baltimore and Seattle. The release of a report is one step in a long process that, in recent years, has typically led to bilateral talks between the department and a city, followed by an agreed-upon police reform plan that’s enforceable by a federal judge.

Such “consent decrees” could end under the incoming Trump administration, analysts have pointed out. The president-elect’s nominee for attorney general, Sen. Jeff Sessions, R-Ala., wrote in 2008 that they “have a profound effect on our legal system as they constitute an end run around the democratic process.”

The scandal over the McDonald video and accusations of a cover-up cost McCarthy his job.

The video, which showed Officer Jason Van Dyke continuing to shoot the teen even as he slumped to the ground, unmoving, provoked outrage. It wasn’t until the day the video was released, more than a year after the shooting, that Van Dyke was charged with murder. He has pleaded not guilty. The next hearing in his case is set for Feb. 3.

In a statement sent minutes before the report was posted online, Fraternal Order of Police President Dean Angelo questioned whether the investigation was compromised because of its timing, with Trump set to take office in one week.

Mayor Rahm Emanuel called the findings “sobering to all of us. Police misconduct will not be tolerated anywhere in the City of Chicago.” Current Superintendent Eddie Johnson said unconstitutional politicing “has no place” in his department or in the city. The Fourth Amendment protects against unreasonable searches and seizures.

The head of the Justice Department’s Civil Rights Division, Vanita Gupta, added that investigations into officers’ actions were “glacially slow” and that discipline of officers was often “unpredictable and ineffective.”

Emanuel also addressed the Justice Department’s conclusion that officers do not have nearly enough supervision. He pointed to his decision to ramp up the number of lieutenants and other supervisors.